INTRODUCTION: Full thickness rotator cuff tears have been associated with changes of the anterior acromion. In a previous study we also documented differences in lateral extension of the acromion in rotator cuff tears compared with shoulders with intact cuffs. It was the purpose of this study to verify in a prospective examination, whether presence or absence of rotator cuff tearing in a precisely defined population is quantitatively related to the degree of lateral extension of the acromion.

MATERIAL AND METHODS: 59 consecutive patients between 60 and 70 years and hospitalized for reasons other than shoulder pathologies were entered into a prospective study. All 110 shoulders without previous operations, major trauma or rheumatoid arthritis were examined radiographically and with ultrasonography by two independent examiners.

RESULTS: 67 cuffs were intact, 28 showed a cuff tendinopathy, 17 a full thickness tearing. The acromion index for shoulder with rotator cuff tear was 0.75, for tendinopathy 0.68 and for normal cuffs 0.65. The differences between rotator cuff tears and the other two groups was significant (p< 0.05). The acromion index was not related to gender or osteoarthritis. An acromion index of < 0.77 had a positive predictive value of > 70%. An acromion index of < 0.7 predicted an absence of rotator cuff tearing with an accuracy of 97%. Interobserver agreement of the assessment was excellent with 88%.

CONCLUSION: The relationship between rotator cuff tears and a large extension of the acromion can be used to predict the presence of rotator cuff tears in shoulders between ages 60 and 70. A cause-effect relation is probable and will be studied further.